Alex Hanff, the campaigns manager at Privacy International, called on the police to explain who will decide how this software will be used in future.
"Once millions and millions of pieces of microdata are aggregated, you end up with this very high-resolution picture of somebody, and this is effectively what they are doing here.
"We shouldn't be tracked and traced and have pictures built by our own government and police for the benefit of commercial gain," he said.
Sarah McSherry, a partner at Christian Khan Solicitors, which represents several protesters in cases against the Metropolitan police, said: "We have already seen the utilisation of a number of tactics which infringe the right to peaceful protest, privacy and freedom of expression, assembly and movement. All of these have a chilling effect on participation in peaceful protest. This latest tool could also be used in a wholly invasive way and could fly in the face of the role of the police to facilitate rather than impede the activities of democratic protesters."
Hugh Tomlinson QC, a specialist in privacy, said a public body such as the police must be able to justify the lawfulness of how it uses the information it collects and retains.
"Storing data because it's potentially interesting or potentially useful is not good enough. There has got to be some specific justification," he said.